BACKGROUND: Hot flashes are a common side-effect of treatment for breast and prostate cancer. Between one-half and two-thirds of breast and prostate cancer patients report hot flashes, and many of these rate their problem as moderately or extremely severe. Several drugs are available, but clinically relevant adverse effects are common and response rates are moderate. Endogenous opioids have been implicated in hot flashes. It is known that acupuncture leads to endorphin release and there is also preliminary evidence that acupuncture may lead to changes in the genetic expression of endogenous opioids. Several single-arm studies have shown large and persistent decreases in hot flashes following acupuncture treatment. A randomized trial in menopausal hot flashes also had encouraging results. These considerations warrant further research on acupuncture for hot flashes associated with cancer treatment. OBJECTIVES: 1. To determine whether a Phase III trial of acupuncture for hot flashes in breast and/or prostate cancer is warranted: 2. To determine whether a Phase III trial is feasible; 3. To determine whether breast and prostate cancer patients should be combined in a single Phase III trial; 4. To determine whether severity of hot flashes need be assessed; 5. To provide data necessary for sample size calculation METHODS: Cancer patients with treatment related hot flashes will complete a diary of hot flashes for one week. They will then be randomized to eight sessions of true or placebo acupuncture over four weeks. Placebo acupuncture consists of a needle that retracts inside its handle, a method that has been shown to be credible to patients. Hot flash diaries will be completed at six, 13 and 26 weeks following randomization. Change in hot flash frequency and hot flash score (frequency multiplied by severity) will be compared by analysis of co-variance. Breast and prostate patients will be accrued and analyzed separately. Data will be combined for exploratory analyses: a test for interaction will be made to determine whether acupuncture has differential effects on hot flashes by type of cancer. At the end of the trial we will have data to address each of our objectives as follows: Objective 1: Confidence interval for the difference between group means; Objective 2: Accrual rate, drop-out rate, compliance with treatment, use of off-study treatments; Objective 3: Interaction between diagnosis and treatment effect, relative accrual and drop-out rate, relative compliance; Objective 4: Correlation between hot flash score and hot flash frequency; Objective 5: Standard deviations, mean of control group, correlation between and within baseline and follow-up measures.